A conventional cellular network is deployed as a homogenous network of macrocell base stations. The macrocell base stations may all have similar antenna patterns and similar high-level transmit powers. To accommodate increases in data traffic, more macrocell base stations can be deployed in a homogenous network, but such a solution is often unattractive due to increased inter-cell interference on the downlink and due to the high costs associated with site acquisition for newly deployed macrocell base stations.
Because of these drawbacks and others, cellular network operators are turning to heterogeneous networks to meet the demands of increased data traffic. In heterogeneous networks, small cell base stations are used to provide small coverage areas that overlap with, or fill in gaps of, the comparatively larger coverage areas provided by macrocell base stations. The small coverage areas are typically provided in areas with high data traffic (or so called hotspots) to increase capacity. Examples of small cell base stations include, in order of decreasing coverage area, macrocell base stations, picocell base stations, and femtocell base stations or home base stations.
There has been a steady increase in the deployment of small cell base stations. In the near future, it is expected that in some areas there will be orders of magnitude more small cell base stations deployed than macro cells. With such high densities (e.g., tens of small cell base stations per square kilometer), the small cell backhaul network used to connect the small cell base stations to the core network, Internet, and other services will be a challenge.
Installing high-capacity, low-latency wired connections from the small cell base stations to the core network would require an exorbitant capital expenditure on the part of network operators. A more economically feasible approach is to implement a wireless backhaul network to link the small cell base stations to the core network. For example, such a wireless backhaul network can link the small cell base stations to the core network via existing macro base stations that already have wired access to the core network. However, the data traffic rate on the wireless backhaul can be very high given that a typical macro base station may be required to relay backhaul data for tens of small cell base stations. Thus, the design and implementation of high data rate wireless backhaul transmissions is important.
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